Solid-state 17O NMR study of the electric-field-gradient and chemical shielding tensors in polycrystalline gamma-glycine.

We report the first experimental determination of the carboxylate oxygen electric-field-gradient (EFG) and chemical shielding (CS) tensors in polycrystalline gamma-glycine. Analysis of magic-angle spinning (MAS) and stationary (17)O NMR spectra of [(17)O]-gamma-glycine obtained at 9.4, 14.1, 16.4, and 18.8 T yields the magnitudes of the (17)O EFG and CS tensors and the relative orientations between the two tensors. Extensive quantum chemical calculations at both the restricted Hartree-Fock and density functional levels have been performed to present the absolute tensor orientations in term of the molecular frame. We have demonstrated that (17)O NMR tensor information could be unambiguously derived by the multiple field analyses of stationary (17)O NMR spectra.